1. Field
The present disclosure relates to zoom lens systems, interchangeable lens apparatuses, and camera systems.
2. Description of the Related Art
In recent years, interchangeable-lens type digital camera systems (also referred to simply as “camera systems”, hereinafter) have been spreading rapidly. Such interchangeable-lens type digital camera systems realize: taking of high-sensitive and high-quality images; high-speed focusing and high-speed image processing after image taking; and easy replacement of an interchangeable lens apparatus in accordance with a desired scene. Meanwhile, an interchangeable lens apparatus having a zoom lens system that forms an optical image with variable magnification is popular because it allows free change of focal length without the necessity of lens replacement.
Compact zoom lens systems having a high zooming ratio and excellent optical performance from a wide-angle limit to a telephoto limit have been desired as zoom lens systems to be used in interchangeable lens apparatuses. Various kinds of zoom lens systems having multiple-unit constructions have been proposed. In each of such zoom lens systems, focusing can be performed by moving some of lens units in the lens system in a direction along the optical axis.
Japanese Patent No. 3054185 discloses a zoom lens having a six-unit construction of positive, negative, positive, negative, positive, and positive, wherein variable magnification is performed by moving the fourth lens unit with the second lens unit being fixed with respect to the object side, and focusing is performed by moving the sixth lens unit.
Japanese Laid-Open Patent Publication No. 10-111455 discloses a zoom lens having a five-unit construction of positive, negative, positive, negative, and positive, wherein at least the fifth lens unit is moved to the object side at the time of zooming to change the intervals between the respective lens units, and the whole or part of the second lens unit or an image blur compensating lens unit is moved to perform focusing.
Japanese Laid-Open Patent Publication No. 2007-279077 discloses a variable magnification optical system having at least a four-unit construction of negative, positive, negative, and positive, wherein at least the second lens unit and the fourth lens unit are moved to change the intervals between the respective lens units. When the variable magnification optical system has a five-unit construction or a six-unit construction, the fifth lens unit is moved to perform focusing.